Tricyclohexylphosphine ligands

Rodriguez and Tenn [68] hydroformylated a dilute ethylene feed with rhodium catalysts based on different trialkylphosphines. With trioctyl-and trihexylphosphine-containing catalysts with respect to the formation of propanol, TOFs of 232-258 h were observed. In contrast, triph-enylphosphine and the more bulky ligands tricyclohexylphosphine and... 

Other Reactions Catalyzed by Metal Complexes Using Tricyclohexylphosphine as a Ligand. Tricyclohexylphosphine plays a key role as a ligand for a number of other metal-catalyzed reactions. These include the use of ... 

Usually, iodides and bromides are used for the carbonylation, and chlorides are inert. I lowever, oxidative addition of aryl chlorides can be facilitated by use of bidcntatc phosphine, which forms a six-membered chelate structure and increa.scs (he electron density of Pd. For example, benzoate is prepared by the carbonylation of chlorobenzene using bis(diisopropylphosphino)propane (dippp) (456) as a ligand at 150 [308]. The use of tricyclohexylphosphine for the carbonylation of neat aryl chlorides in aqueous KOH under biphasic conditions is also recommended[309,310]. 

The delta lactone can be obtained in very high yields when triisopropylphosphine or tricyclohexylphosphine is the ligand along with Pd(acac)2 as the metal source (171). 

The stereochemistry of reduction by homogeneous catalysts is often controlled by functional groups in the reactant. Delivery of hydrogen occurs cis to a polar functional group. This behavior has been found to be particularly characteristic of an iridium-based catalyst that contains cyclooctadiene, pyridine, and tricyclohexylphosphine as ligands, known as the Crabtree catalyst 6 Homogeneous iridium catalysts have been found to be influenced not only by hydroxy groups, but also by amide, ester, and ether substituents.17... 

Very subtle ligand effects have been detected in these reactions. Thus, under the same conditions, 1 mole of tricyclohexylphosphine and 1 mole of Ni(COD)2 in the presence of excess morpholine catalyze addition of acetophenone to 2 moles of butadiene to give compound A below, whereas triphenylphosphine gives B. With triphenylphosphite C—C coupling no longer occurs, but morpholine adds to butadiene to give C (135). 

Recently, the groups of Fu and Buchwald have coupled aryl chlorides with arylboronic acids [34, 35]. The methodology may be amenable to large-scale synthesis because organic chlorides are less expensive and more readily available than other organic halides. Under conventional Suzuki conditions, chlorobenzene is virtually inert because of its reluctance to oxidatively add to Pd(0). However, in the presence of sterically hindered, electron-rich phosphine ligands [e.g., P(f-Bu)3 or tricyclohexylphosphine], enhanced reactivity is acquired presumably because the oxidative addition of an aryl chloride is more facile with a more electron-rich palladium complex. For... 

Thus far, considerably more research has been directed towards RCM in water. The majority of metathesis catalysts decompose rapidly in the presence of water or oxygen, however, Grubbs s ruthenium based catalysts are quite robust. Replacement of the tricyclohexylphosphine ligands with water soluble phosphines has allowed their deployment in aqueous-organic biphasic processes although conversions are often not as good as those obtained in other solvents [18]. 

As a polar solvent for the catalyst ethylene carbonate (EC), propylene carbonate (PC) and acetonitrile were used. Tricyclohexylphosphine, triphenyl-phosphine and the monosulfonated triphenylphosphine (TPPMS) were investigated as ligands with Pd(acac)2 as the precursor. Cyclohexane, dodecane, p-xylene and alcohols (1-octanol, 2-octanol and 1-dodecanol) were tested as non-polar solvents for the product. To determine the distribution of the product and of the catalyst, the palladium precursor and the hgand were dissolved in the polar solvent and twice as much of the non-polar solvent was added. After the addition of 5-lactone, the amounts of the product in both phases was determined by gas chromatography. The product is not soluble in cyclohexane and dodecane, more than 99% of it can be found in the polar catalyst phase. With the alcohols 1-octanol, 2-octanol and dodecanol about 50 to 60% of the 5-lactone are located in the non-polar phase. With p-xylene biphasic systems can only be achieved when EC is used as the polar solvent and even in this solvent system one homogeneous phase is formed at a temperature higher than 70 °C. In a 1 1 mixture of EC and p-xylene about 50 to 60% of the product is contained in the polar phase. 

The distribution of the catalyst depends on the choice of the non-polar solvent and on the ligand used. With cyclohexane and the alcohols the palladium complexes of tricyclohexylphosphine and triphenylphosphine are located in the polar phase, with p-xylene the complex of triphenylphosphine is dispersed in both phases, and the complex of tricyclohexylphosphine can be predominantly found in the non-polar phase. Because of the low solubility of... 

To investigate the use of a non-polar catalyst phase and a polar product phase EC, PC and acetonitrile were chosen as polar solvents and cyclohexane and p-xylene as non-polar solvents. Tricyclohexylphosphine, triphenylphos-phine and bisadamantyl-n-butyl-phosphine were used as the ligand for Pd(acac)2. If cyclohexane is used as the non-polar solvent, the palladium complexes of tricyclohexylphosphine and triphenylphosphine are situated in the polar solvent and with p-xylene the complex of tricyclohexylphosphine is located in the non-polar phase, hi the solvent system EC/cyclohexane the palladium complex of bisadamantyl-n-butyl-phosphine can be found in the cyclohexane phase. 

The results of this analysis of the product and catalyst distribution show that only a limited range of systems may be apphcable for the telomeriza-tion of butadiene and carbon dioxide. The reaction was performed in the biphasic systems EC/2-octanol, EC/cyclohexane and EC/p-xylene. The yield of 5-lactone reached only 3% after a reaction time of 4 hours at 80 °C. hi the solvent system EC/2-octanol triphenylphosphine was used as the hgand. With the ligand bisadamantyl-n-butyl-phosphine even lower yields were achieved in a single-phase reaction in EC or in the biphasic system EC/cyclohexane. The use of tricyclohexylphosphine led to a similar result, only 1% of the desired product was obtained in the solvent system EC/p-xylene, which forms one homogeneous phase at the reaction temperature of 80 °C. Even at a higher temperature of 100 °C and a longer reaction time of 20 hours no improvement could be observed. Therefore, we turned our interest to another telomerization-type process. 

Significant advances in organonickel chemistry followed the discovery of frtzws,fraws,fraws-(l,5,9-cyclododecatriene)nickel, Ni(cdt), and bis(l,5-cycloocta-diene)nickel Ni(cod)2 by Wilke et. al.1 In these and related compounds, in which only olefinic ligands are bonded to the nickel, the metal is especially reactive both in the synthesis of other compounds and in catalytic behavior. Extension of this chemistry to palladium and to platinum has hitherto been inhibited by the lack of convenient synthetic routes to zero-valent complexes of these metals in which mono- or diolefins are the only ligands. Here we described the synthesis of bis(l,5-cyclooctadiene)platinum, tris(ethylene)-platinum, and bis(ethylene)(tricyclohexylphosphine)platinum. The compound Pt(cod)2 (cod = 1,5-cyclooctadiene) was first reported by Muller and Goser,2 who prepared it by the following reaction sequence ... 

Immirzi and Musco209 have proposed a modification of Tolman s definition of cone angle to account for the ability of ligands to intermesh when complexed, e.g. tricyclohexylphosphine in... 

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